With seals between relatively moving machine components, the danger exists that the components may approach one another to a point where severe friction between the components may cause excessive heating and possible destruction of the seal. This is a particular problem in gas turbine engines which have many high speed components rotating relative to stationary components carrying sealing elements thereon.
In one attempt to address this problem, an abradable coating has been provided on the stationary component or rotating component. The coating is gradually worn away by contact with the other component and, as a result, the clearance between the components is increased and sealing efficiency is reduced.
In another attempt to solve this problem, a so-called brush seal is carried on one of the machine components and includes tightly packed bristles to engage the other adjacent component rotatable relative thereto to effect fluid sealing between the components. U.S. Pat. Nos. 885,032; 2,878,048; 4,202,554; 4,358,120; and U.S. Reissue No. 30,206 illustrate such brush seals. Various fabrication techniques have been employed to make such brush seals. Many of these fabrication techniques are slow, costly and labor intensive. U.S. Pat. No. 4,415,309 illustrates a technique for fabricating a brush seal for a gas turbine engine wherein the sealing element is formed as a woven fabric having metallic warp filaments, metallic weft filaments and metallic warp pile filaments. A portion of the fabric formed of the warp and weft filaments is brazed to one component of the gas turbine engine. The warp pile filaments are cut to form a brush seal for engaging the other component of the gas turbine engine.
Copending U.S. application Ser. No. 321,370 filed Mar. 9, 1989, of common assignee herewith discloses a three dimensionally braided filamentary sealing element for use between components in a gas turbine engine or other machine where a clearance space is provided between the components.